OmegaPoint Coding Test

Here are the fully tested solutions to the coding test, it took another 20 minutes to complete the testing and to optimize them in RStudio.

1. In a childrens game, the kids count off around the circle they are sitting in. When their number is divisible by 3 they say fiz, by 5, they say buz, when both, they say fizbuz, otherwise they say their number.

fizbuz<-function(){  #vectorized is faster
    r<-seq(100)
    r3<-!r%%3
    r5<-!r%%5
    r[r3]<-"fiz"
    r[r5]<-"buz"
    r[r3&r5]<-"fizbuz"
    return(r)
}# end function fizbuz
fizbuz()

##   [1] "1"      "2"      "fiz"    "4"      "buz"    "fiz"    "7"     
##   [8] "8"      "fiz"    "buz"    "11"     "fiz"    "13"     "14"    
##  [15] "fizbuz" "16"     "17"     "fiz"    "19"     "buz"    "fiz"   
##  [22] "22"     "23"     "fiz"    "buz"    "26"     "fiz"    "28"    
##  [29] "29"     "fizbuz" "31"     "32"     "fiz"    "34"     "buz"   
##  [36] "fiz"    "37"     "38"     "fiz"    "buz"    "41"     "fiz"   
##  [43] "43"     "44"     "fizbuz" "46"     "47"     "fiz"    "49"    
##  [50] "buz"    "fiz"    "52"     "53"     "fiz"    "buz"    "56"    
##  [57] "fiz"    "58"     "59"     "fizbuz" "61"     "62"     "fiz"   
##  [64] "64"     "buz"    "fiz"    "67"     "68"     "fiz"    "buz"   
##  [71] "71"     "fiz"    "73"     "74"     "fizbuz" "76"     "77"    
##  [78] "fiz"    "79"     "buz"    "fiz"    "82"     "83"     "fiz"   
##  [85] "buz"    "86"     "fiz"    "88"     "89"     "fizbuz" "91"    
##  [92] "92"     "fiz"    "94"     "buz"    "fiz"    "97"     "98"    
##  [99] "fiz"    "buz"

2. Swap upper and lower case characters, leave non-characters as is.

swapUL<-function(string) {
    b<-unlist(strsplit(string,""))
    low<-b %in% letters
    high<-b %in% LETTERS
    b[low]<-toupper(b[low])
    b[high]<-tolower(b[high])
    return(paste(b, sep="", collapse=""))
}
swapUL("abcDEF123")

## [1] "ABCdef123"

3. Generate all permuations of a given string

# show R package and function used.
library(gtools)
permutations(3, 3, letters[1:3])

##      [,1] [,2] [,3]
## [1,] "a"  "b"  "c" 
## [2,] "a"  "c"  "b" 
## [3,] "b"  "a"  "c" 
## [4,] "b"  "c"  "a" 
## [5,] "c"  "a"  "b" 
## [6,] "c"  "b"  "a"

#string<-"abc"
perms<-function(string){
    #string<-"abc"
    b<-unlist(strsplit(string,""))
    len<-length(b)
    p<-permutations(len, len, b)
    pa<-apply(p,1,paste,sep="",collapse="")
    return(pa)
}
perms("abcd")

##  [1] "abcd" "abdc" "acbd" "acdb" "adbc" "adcb" "bacd" "badc" "bcad" "bcda"
## [11] "bdac" "bdca" "cabd" "cadb" "cbad" "cbda" "cdab" "cdba" "dabc" "dacb"
## [21] "dbac" "dbca" "dcab" "dcba"